[DMCForum] steering geometry. was Re: Speak slowly, use small words (On Topic)

["cruznmd" <racuti1@xxxxxxxxxxxx>]

Very cool Rick. Thanks!

I did have extensive welding done up front due to rust.
The crumple tube bottom was toast.

Part of the frame, specifically, the "Y" uh, the part that the 
crumple tube mounts to, the part that closes off the Y was rusted 
away in the center. Not completely, but it wasn't good. Am I making 
sense?

The welder replaced the metal in the center with cast iron, square 
tubing from an old automobile frame he had. He said this was 
necessary to keep the lower control arms from shifting. Because the 
metal wasn't completely gone, I believe that nothing had shifted yet 
and his repair is good.

If the camber is negative, it's not so bad that I can tell just by 
looking at the wheels. I'd have to use the roofing square. It took 
months of driving for the tire wear to manifest.

Jeeze I wish those tie-rod ends would get here so I can get aligned.
They're in the mail.

Rich
#5335


--- In DMCForum@xxxxxxxxxxxxxxx, "twinenginedmc12" 
<twinenginedmc12@xxxx> wrote:
> --- In DMCForum@xxxxxxxxxxxxxxx, "cruznmd" <racuti1@xxxx> wrote:
> > Someone please explain DeLorean steering geometry to me. I am 
> > familiar with some terms: Toe, caster and camber.
> > 
> > Due to the wear on the inner edges of my tires, I suspect they 
are 
> > pointed like this:   //  \\  (If you're looking at the car head-
on)
> > 
> > Instead of: ||   ||  (Ditto)
> > 
> > Which of the above 3 is responsible for this, and is it 
adjustable 
> in 
> > the DeLorean?
> > 
> > My new tie-rod ends will be here soon and I'm going to take it to 
> the 
> > alignment joint up the road Friday morning. Before I do, I want 
to 
> > know if I have something else that's really wrong.
> > 
> > I have read the tech section of DMC news and a few other places 
and 
> > find the explanations lacking. 
> > 
> > Thanks,
> > 
> > Rich A.
> > #5335
> 
> Hi Rich.
> 
> Inner edge tire wear would mostly be caused by excessive negative 
> camber (wheels pointed like this:   //  \\ if you're looking at the 
> car head-on), like you said earlier, or misaligned wheels, with toe 
> out(wheels pointing away from each other in front) 
> You can check camber easily yourself, with only a roofing square 
> (24"x18" "L" shaped right angle) for tools.
> 
> Camber measurement
> Simply find a flat level piece of parking lot, and roll the car to 
a 
> coasting straight line stop on it.  Don't use the front brakes 
> stopping, the brake force changes the steering geometry. Place one 
> edge of the roofing square against the ground pointing away from 
the 
> tire, and the other edge against the tire, pointing upwards, away 
> from the ground.  Avoid the part of the tire that's squished 
outwards 
> at the point where the tire touches the ground.  I personally put 
it 
> as close to the middle of the wheel as I can, while avoiding the 
> contact patch bulge.
> Look for a gap between the roofing square and the tire. If there's 
a 
> big gap at the top part of the tire between the roofing square and 
> the tire, the camber is excessively negative.  
> If there's a big gap at the bottom part of the tire between the 
> roofing square and the tire, the camber is excessively positive.
> If the roofing square touches the tire at the top and bottom of the 
> rim, the camber is neutral.
> Most cars are specified to have neutral, or very slightly negative 
> camber.  I don't know the Delorean specification.
> 
> Since Deloreans don't have adjustable camber, if you find that the 
> camber is excessively negative, your car has problems, something 
bent 
> or broken or worn out.  If your camber is okay, it's very likely 
> incorrect toe.  That's what my money is on, since it's the only 
thing 
> that's really adjustable, and you haven't crashed your car yet, 
which 
> suggests that the suspension is still mostly intact.
> 
> Toe is a little harder to check yourself, but it can also be done.  
> 
> I wouldn't worry about the caster, since it is not adjustable, and 
is 
> much less likely to get screwed up from suspension damage than 
camber
> 
> Since people who lower their cars don't complain about this wear 
> problem, it's likely that ride height doesn't affect this wear, so 
> springs or shocks are also less likely culprits.
> 
> As an aside, the three different parameters, camber, caster, and 
toe, 
> all interact.  If more than one is wrong at a time, it gets really 
> hard to diagnose tire wear.  If you make changes, make small 
changes 
> to only one at a time, and assess the effect.
> 
> Rick.

---

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